At the time of this comment the title of this post is "Global Warming Not Caused by CO2". I wish I could vote the post down more often. I just read the linked paper and is says nothing of that sort, and can't by its methodology. The paper tries to measure feedback effects and concludes that they can't be measured by the methodology they have chosen, but it looks like they are much lower than assumed in most climate models. They don't, and can't, say anything about the direct effect of CO2.

In essence they take measurements of net radiation flux and of temperature changes and try to figure out which changes which. They call variations in radiation flux not caused by temperature forcing, and those that are caused feedback (since radiation flux is a measure of how much energy is flowing into or out of the system radiation flux changes will always cause temperature changes). They conclude that they can't say anything definite because of the numbers of factors involved ("a variety of parameters other than feedback affecting the lag regression statistics which make accurate feedback diagnosis difficult"), but that it looks like most of the variation can be ascribed to forcing. Forcing would include the direct effect of CO2. Of course the climate models mostly assume strong positive feedback, so absence of such feedback would mean less CO2 caused warming overall, but the current title is a complete mischaracterization of the actual results.